Elastomeric electrical cable accessories are typically installed over cables, metallic contacts or mated in complimentary designs such as elbows and bushings, connectors, splices, switches, fuses, junctions and a wide variety of other configurations. In almost every design, installation requires interfaces to slide against each other with corresponding frictional forces. Because these components are elastomeric, these frictional forces are very high. Thus lubrication of these interfaces is a necessity. The most common lubricants are oils and greases, typically based on a compatibility with the type of elastomer requiring lubrication. Silicone oils and greases exhibit excellent electrical characteristics and are very compatible with ethylene-propylene based elastomers. These lubricants are usually supplied by the manufactures at significant cost as a separate package with the cable accessories.
A large majority of cable accessories are based on ethylene-propylene elastomers such as ethylene-propylene rubber (EPR) and ethylene propylene diene monomer (also referred to as ethylene propylene diene methyl or EPDM) and are typically lubricated with silicone-based oils and greases. EPR is a thermoset material synthesized from ethylene, propylene and, in many instances, a third monomer. If only ethylene and propylene are used, the polymer may be referred to as EPM. If three monomers are used, the resulting polymer is called EPDM. Peroxide is the predominant cross-linking agent for EPR compounds.
Cable accessories have a 30- to 40-year life, and many have separable interfaces used for connection and disconnection. Although many oils and greases are high quality and are used effectively for many years of service, they often lose their lubricating capacity over time. Due to the inherent mobility of the oils used in these lubricants, they tend to “bleed” and/or migrate away from the interface. Consequently, the interface “dries out” and exposes the high coefficient of friction elastomeric surface. The result is component sticking which is deemed a major problem in the industry.
Accordingly, there is a need for a more reliable and cost-effective formulated coating and application process to provide a more permanent lubricated surface to an elastomeric electrical cable accessory.